Former Hartford Mayor Antonina “Ann” Uccello announces that she is seeking the Republican nomination for the 1st Congressional district seat left vacant by the death of Rep. William R. Cotte, on Dec. 7, 1981. Stephen Dunn/Hartford Courant via AP

HARTFORD, Conn. — Antonina “Ann” Uccello, the first woman to be elected a mayor in Connecticut when she won an upset victory as a Republican in Hartford in 1967, has died. She was 100.

Uccello, who went on to serve in the Nixon, Ford and Carter administrations, died of natural causes Sunday night at a hospital in Hartford, said Jacqueline Gustafson, who is married to Uccello’s nephew, David Gustafson.

“She just had remarkable intellect, resiliency and determination,” Jacqueline Gustafson, of West Hartford, said in a phone interview Tuesday. “She was someone I greatly admired. … Ann was always someone I could talk to.”

Tributes from state political leaders poured in Tuesday afternoon as word of Uccello’s passing began circulating.

“Ann Uccello was a trailblazer who was born and raised in Hartford and dedicated her career in public service to the city she loved,” Democratic Gov. Ned Lamont said in a statement. “She had a remarkable spirit and energy, and she leaves a lasting legacy on Connecticut’s capitol city.”

Lt. Gov. Susan Bysiewicz, also a Democrat, said Uccello shattered glass ceilings in the Connecticut political arena, then served as one of the highest-ranking women in the Nixon administration – as consumer affairs director in the Department of Transportation. She continued to work at the Transportation Department under Presidents Gerald Ford and Jimmy Carter.

“I admired her ground breaking work as Mayor of Hartford,” Bysiewicz said in a statement. “She leaves a legacy that has and will continue to inspire generations of women to pursue careers in politics and public service.”

Uccello, who has a street named after her in Hartford, served on the city council from 1963 to 1967 after working as a high school history teacher and in management positions at the G. Fox department store. In a heavily Democratic city, she defeated incumbent Mayor George Kinsella in the 1967 election and was re-elected two years later.

As mayor, she was best known for comforting city residents and helping to prevent riots after the assassination of Martin Luther King Jr. in 1968, according to Connecticut Women’s Hall of Fame, where she was inducted in 1999. She also worked to protect children from lead poisoning and helped create low- and moderate-income housing, according to the Hall of Fame.

Uccello also ran for the 1st Congressional District in the Hartford area in 1970, but lost a close race to Democrat William Cotter before taking the Department of Transportation job.

Uccello was one of five daughters of immigrants from Sicily, Italy. After graduating from high school and then a private Roman Catholic college, she did graduate work at Trinity College in Hartford and the University of Connecticut Law School.

She was a devout Christian and never married, Jacqueline Gustafson said.

Gustafson said she once asked Uccello why she never married and Uccello responded, “I never met a man who deserved that much happiness.”

Gustafson said Uccello’s funeral is expected to be held next week and she will be buried at the historic Cedar Hill Cemetery in Hartford, the final resting place of many notable Hartford residents and natives including actress Katharine Hepburn.